This proposal is a request for funds to hold a 3-day international workshop of investigators whose research is aimed at understanding the basis for the strong association of HLA-B27 with spondyloarthritis. This very strong genetic association has been known for 35 years, but the mechanism remains unknown and many different hypotheses continue to be entertained. The specific objectives of the proposed workshop are: [1] Through the use of background summaries and brief overview presentations, to clarify the current state of knowledge regarding HLA-B27 and the current hypotheses to explain its role in spondyloarthritis [2] Through extensive guided discussions, to identify gaps in knowledge, refine and extend existing hypotheses, and formulate research goals toward which the field should move [3] Through continued discussions, to establish collaborations and/or consortia, and to identify funding opportunities that would advance pursuit of these goals [4] To attract and maintain the interest of young investigators in this field The overall goal is to hasten the day when a detailed molecular understanding of the role of HLA- B27 in spondyloarthritis. Accomplishing this goal is expected to lead to improved means of prevention and treatment of this important and common group of rheumatic diseases.